Alternate Resources?How do...

Alternate Resources?
How do I change to an Alternate Resource, when issuing a Resource transaction?
I am setting up a pilot WIP environment for a customer. For a given product we have a route, where the first operation can actually be completed on five different machines (resources).
I have a "primary resource" defined for the product, but production planning should have the option of switching to anyone of the other 4 resources.
I have set up the operation with one resource an 4 alternates.
In the Discrete Jobs. I can see the job order, and the primary resource. When clicking Alternates the 5 other resources are shown.
But how do I actually change to an alternate resource? In the Resource transaction form, it is only possible to select the primary resource.
Attached images showing setup

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